JPH06117432A - Two-way dynamic pressure fluid bearing - Google Patents

Abstract

PURPOSE:To provide a two-way dynamic pressure fluid bearing capable of being used as a bearing for supporting the rotary shaft of a precision rotating device like a gas turbine, a compressor, an inertial guiding high-precision gyroscope or the like under high peripheral speed condition, and forsupporting a rotary shaft rotatably in the non-touching state even if the rotational sdirection of the rotary shaft is the normal direction or the riverse direction. CONSTITUTION:Spiral grooves 10, 11 extending from the external circumferential edges on the internal circumferential edges of sliding surfaces 5, 6 as base ends and closing their ends and having the approximately mirror image relationship are respectively providing on both mutually opposing and connected sliding surfaces 5, 6 between a rotary ring 3 fixed to a rotary shaft 2 and a non-rotary ring 4 fixed to housing 1 and dynamic pressure is generated by the spiral grooves on one sliding surface in accordance with the normal directional rotation of the rotary shaft, while the dynamic pressure is generated by the spiral grooves on the other sliding surface in accordance with the reverse directional rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a hydrodynamic bearing, and more particularly, to a high-performance bearing for supporting a rotary shaft of a precision rotating device such as a gas turbine, a compressor or an ultra-precision gyro for inertia induction. The present invention relates to a bidirectional hydrodynamic bearing that can be used under high speed conditions.

[0002]

2. Description of the Related Art Conventionally, a dynamic pressure gas bearing has been used as a bearing for supporting a rotating shaft in a precision rotating device such as an inertial super-precision gyro. This dynamic pressure gas bearing has one of the sliding surfaces facing each other of the rotating ring fixed to the rotating shaft and the non-rotating ring fixed to the housing,
A large number of spiral grooves of the same length that have an advancing angle with respect to the relative rotation direction are provided at regular intervals in the circumferential direction, and gas is pressure-fed between the sliding surfaces by these spiral grooves, and a minute amount is provided between both sliding surfaces. Since it forms a gap and is rotatably supported, both sliding surfaces are in non-contact state, so even under high-speed rotation, that is, high peripheral speed conditions, there is little wear and friction resistance on the sliding surface, and seizure does not occur. Of.

However, in the conventional dynamic pressure gas bearing, the above-mentioned non-contact state is created only when the rotating ring rotates in a specific forward direction with respect to the non-rotating ring. The fluid is discharged from the chamber, the pressure drops, and a vacuum state is established, so that both sliding surfaces are in firm contact with each other.

Although the above-mentioned problem does not occur in the rotating device in which the rotating shaft rotates only in the forward direction, in the actual operation of the compressor or the like, the rotating ring normally rotates in the set forward direction. However, reverse rotation often occurs at the initial stage of rotation or immediately before stopping. In that case, since the two sliding surfaces are in strong contact with each other, the sliding surfaces are often worn and frictional heat is generated, which may impair the characteristics of the surfaces.

On the other hand, even in the case of rotating only in the forward direction, in order to support both ends of the rotating shaft which penetrates the housing, the arrangement of the rotating ring and the non-rotating ring in the axial direction of the rotating shaft is reversed. Therefore, the spiral groove formed on the sliding surface must be formed to have an advancing angle in the opposite direction. This means that two kinds of symmetrical dynamic pressure gas bearings are required, which leads to an increase in cost.

It is to be noted that the spiral groove formed on the sliding surface exerts its original dynamic pressure generating function under high speed rotation conditions above a certain level, and at low speed, sufficient dynamic pressure is not generated. Both sliding surfaces remain in contact.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned situation, the present invention is to solve the problems regardless of whether the rotating direction of the rotating ring with respect to the non-rotating ring is the forward direction or the reverse direction. In addition to providing a bidirectional hydrodynamic bearing that can generate dynamic pressure between the sliding surfaces by the spiral groove formed on the sliding surfaces and can rotatably support both sliding surfaces in a non-contact state, Thus, the present invention provides a bidirectional hydrodynamic bearing that has low rotational friction resistance even under low-speed rotation conditions.

[0008]

In order to solve the above-mentioned problems, the present invention provides, as a first invention, a pair of sliding surfaces on which a rotating ring fixed to a rotating shaft and a non-rotating ring fixed to a housing are in contact with each other. , Extending with its outer peripheral edge or inner peripheral edge as the base end,
Spiral grooves that are close to each other and have a substantially mirror image relationship are provided, and dynamic pressure is generated in the spiral groove of one sliding surface with forward rotation of the rotating shaft, and the other slides with reverse rotation. A bidirectional hydrodynamic bearing was constructed by generating dynamic pressure in the spiral groove of the surface.

The dam width ratio of the spiral groove is about 0.2 to.
It was set to 0.8. And, in order to seal between the rotary shaft that normally rotates only in the forward direction and the housing, the number of spiral grooves having an advance angle with respect to the relative rotation direction due to the forward rotation of the rotary shaft is set to the other. Either more was set or its width was set wider than the other or its depth was set deeper than the other. Further, in order to seal between the rotary shaft that rotates in either the forward direction or the reverse direction and the housing, the spiral grooves formed on the both sliding surfaces have a perfect mirror image relationship.

As a second aspect of the invention, the sliding surfaces of the rotating ring fixed to the rotating shaft and the non-rotating ring fixed to the housing are opposed to each other and extend with the outer peripheral edge or the inner peripheral edge as the base end, and the terminal ends thereof. Providing closed spiral grooves that are substantially mirror images of each other, dynamic pressure is generated in the spiral groove of one sliding surface with forward rotation of the rotary shaft, and spiral of the other sliding surface with reverse rotation. A bidirectional hydrodynamic bearing that generates dynamic pressure in a groove, wherein a plurality of inlets provided between two O-ring grooves formed on the outer peripheral end surface of the non-rotating ring and a plurality of inlets provided on a sliding surface are provided. Of the non-rotating ring are connected to each other through a conduction path formed in the non-rotating ring, and when the O-ring is fitted into the O-ring groove and hermetically fixed to the inner wall of the housing, the above-mentioned outer side of the outer peripheral end surface of the non-rotating ring is To form an annular sealed space that communicates with each inlet O-ring an annular groove formed in the inner wall corresponding to between, to constitute a further bidirectional hydrodynamic bearing fluid supply path for supplying obtained by forming communication in a housing of the high pressure fluid to the annular groove.

It is preferable that the jet outlet is formed on a flat surface which is a sliding surface and does not form a spiral groove.
Further, it is also possible to open the jet port in a circular flow path which is a sliding surface and intersects each spiral groove and is formed deeper than the depth of the spiral groove.

As a third aspect of the invention, a first non-rotating ring and a second non-rotating ring are hermetically attached to the inner wall of the housing with a rotating ring fixed to the rotating shaft interposed between the rotating ring and each non-rotating ring. Spiral grooves extending from the outer peripheral edge as a base end and closed at their ends are provided respectively on both sliding surfaces that are in contact with the ring. Dynamic pressure is generated in the spiral groove of one sliding surface of the sliding surface formed on both sides or one surface of each non-rotating ring, and in the spiral groove of the other sliding surface due to reverse rotation. A bidirectional hydrodynamic bearing for generating dynamic pressure, wherein a fluid supply path for supplying high-pressure fluid to a space surrounded by the outer peripheral end surface of the rotating ring, each non-rotating ring and the inner wall is communicated with the housing. Bi-directional hydrodynamic fluid formed You configure the receive.

Then, the first non-rotating ring located inside the housing is stopped by the stepped portion provided on the inner wall, and the second non-rotating ring located outside is pressed inward. It is preferable to interpose a pressing metal member made of ???

[0014]

The bidirectional hydrodynamic bearing of the present invention having the above-mentioned contents has the sliding surface of the rotating shaft and the sliding surface of the non-rotating ring,
Fluid transport by the spiral groove formed on one sliding surface with forward rotation by providing spiral grooves that extend from the outer peripheral edge or the inner peripheral edge as a base end and close the end and are in a substantially mirror image relationship with each other. By the action, the fluid is pumped between the sliding faces, and by the fluid transport action by the spiral groove formed on the other sliding face with the reverse rotation, the fluid is also pumped between the sliding faces by the action of the rotating shaft in the forward direction. Alternatively, even if the sliding surfaces rotate in opposite directions, both sliding surfaces are rotatably supported in a non-contact state.

Further, the number of spiral grooves having an advancing angle with respect to the relative rotation direction due to the forward rotation of the rotary shaft is set larger than the other, the width thereof is set wider than the other, or the depth thereof is set. By setting it deeper than the other, the dynamic pressure generation performance is improved when the rotating shaft is rotating in the forward direction, and when the rotating shaft rotates in the opposite direction when the rotating shaft stops, both sliding surfaces are The non-contact state is maintained to the extent that it does not come into solid contact.

When the spiral grooves formed on both the sliding surfaces have a perfect mirror image relationship, substantially the same movement is achieved regardless of whether the rotating shaft rotates in the forward direction or in the reverse direction. It has pressure generation performance.

Further, in the above-described bidirectional hydrodynamic bearing, a plurality of inlets formed between two O-ring grooves formed on the outer peripheral end surface of the non-rotating ring and a plurality of jet outlets formed on the sliding surface are provided. When the O-ring is fitted into the non-rotating ring and the O-ring is fitted into the O-ring groove and is hermetically fixed to the inner wall of the housing, the introduction port is provided outside the outer peripheral end face of the non-rotating ring. By forming an annular groove in the inner wall corresponding to both O-rings to form an annular sealed space that communicates with each other, and further by forming a fluid supply path for supplying a high-pressure fluid to the annular groove in the housing, The fluid is forced to flow between both sliding surfaces to maintain the non-contact state between both sliding surfaces even at low speed rotation where the dynamic pressure generation performance due to the spiral groove is low, or to sufficiently reduce the contact friction resistance. It is possible.

In this case, if the jet outlet is formed on a flat surface which is a sliding surface and does not form a spiral groove, a high pressure fluid jetted from the jet outlet can efficiently form a fluid film between the sliding surfaces. Further, when the jet outlet is formed in the annular flow passage which is a sliding surface and intersects with each spiral groove and is formed deeper than the depth of the spiral groove, a high pressure is uniformly applied between the sliding surface through the spiral groove from the annular flow path. Fluid can flow in.

Further, the first non-rotating ring and the second non-rotating ring are hermetically attached to the inner wall of the housing with the rotating ring fixed to the rotating shaft interposed therebetween, and the rotating ring and each non-rotating ring are paired with each other. Spiral grooves, which extend from the outer peripheral edge as a base end and are closed at their ends, are provided in the sliding surfaces in contact with each other and are in a substantially mirror image relationship, and are surrounded by the outer peripheral end surface of the rotating ring, each non-rotating ring and the inner wall. The fluid supply path for supplying high-pressure fluid to the space to be communicated is formed in the housing, so that the fluid is forced to flow between the two pairs of sliding surfaces from the outer peripheral end side of the spiral groove, and the same as above. It is designed to be applicable even at low speed rotation.

In this case, the first non-rotating ring located inside the housing is stopped by the stepped portion provided on the inner wall, and the second non-rotating ring located outside is pressed inward. By interposing a pressing metal fitting consisting of a spring on the outer peripheral edge of the second non-rotating ring and mounting it on the housing with an annular fixing tool, the gap between the two sliding surfaces can be automatically adjusted. is there.

[0021]

The present invention will be described in more detail with reference to the embodiments shown in the accompanying drawings. FIG. 1 shows the overall structure of a bidirectional hydrodynamic bearing H according to the first invention, which is provided between a housing 1 and a rotary shaft 2 penetrating an open end of the housing 1. As the "fluid" in the present invention, air is usually used, but other types of gas or liquid can also be used.

The bidirectional hydrodynamic bearing H of the first invention comprises a rotating ring 3 fixed to the rotating shaft 2 and the housing 1.
The non-rotating ring 4 fixed to the above is provided, and the sliding surfaces 5 and 6 of the rotating ring 3 and the non-rotating ring 4 are in contact with each other.
Here, the non-rotating ring 4 has a central hole 8 having a larger inner diameter than the central hole 7 of the rotating ring 3, and a concentric step portion 9 is formed on the outer peripheral edge facing the rotating ring 3. The dimension is set so that the inner edge of the stepped portion 9 and the outer edge of the rotating ring 3 are substantially coincident with each other, and the common surface where the rotating ring 3 and the non-rotating ring 4 overlap is used as the sliding surfaces 5 and 6 described above. .

Then, as shown in FIG. 2, the rotating ring 3
The sliding surface 5 is provided with a large number of spiral grooves 10 extending inward from the outer peripheral edge thereof and having an advance angle with respect to a specific rotation direction (forward direction) in the circumferential direction at regular intervals. On the other hand, as shown in FIG. 3, on the sliding surface 6 of the non-rotating ring 4, a spiral groove 11 extending inward from its outer peripheral edge and having a receding angle with respect to the relative rotation direction with respect to the forward rotation. Are provided in the circumferential direction at regular intervals. That is, the spiral groove 10 and the spiral groove 11 are formed so as to have a substantially mirror image relationship with each other when both sliding surfaces 5 and 6 are in contact with each other. here,
The inner ends of the spiral grooves 10 and 11 are closed, i.e. flush with the flat surfaces 12 and 13 of the sliding surfaces 5 and 6.
The relationship between the advancing angle and the advancing angle with respect to the relative rotation direction of the spiral grooves 10 and 11 may be reversed.

The fixing of the rotary ring 3 to the rotary shaft 2 is as follows.
A fixed sleeve 1 in which a center hole 7 is fitted and stopped in an annular step portion 14 formed on the rotary shaft 2 and coaxially externally inserted from the outside in the axial direction.
Screw part 17 in which the fastener 16 is formed on the rotary shaft 2 through
It is tightened by screwing on. The fixed sleeve 15 and the fastener 16 are located radially inward of the central hole 8 of the non-rotating ring 4. However, the fixing means of the rotating ring 3 is not limited to this embodiment.

The non-rotating ring 4 is fixed to the housing 1 by fitting the outer peripheral end surface 20 of the non-rotating ring 4 to the cylindrical inner wall 18 of the housing 1 and at the annular step portion 19 formed on the inner wall 18. While the step portion 9 of the non-rotating ring 4 is stopped, the annular fixing member 22 is fastened to the end surface 21 of the housing 1 with the bolt 23, so that the annular fixing member 22 is projected on the inner peripheral portion of the annular fixing member 22. The outer peripheral edge 25 of the non-rotating ring 4 is pressed by the flange portion 24. However, the fixing means of the non-rotating ring 4 is not limited to this embodiment.

2 and 3 show a spiral groove 10 formed on the sliding surfaces 5 and 6 of the rotating ring 3 and the non-rotating ring 4 of the present invention.
An example of the patterns of Nos. 11 and 11 is shown, respectively, and the one shown in the figure is one in which both spiral grooves 10 and 11 are formed in a perfect mirror image relationship. Next, the dam width ratio is defined by the following equation.

[Equation 1] Dam width ratio = (GD-ID) / (OD-ID)

## EQU00002 ## Dam width ratio = (OD-GD) / (OD-ID) where OD is the outer diameter of the common part of the sliding surfaces 5 and 6, ID is the inner diameter, and GD is the groove area of the spiral groove. It is the diameter of the contour circle formed at the boundary with the flat region. Formula 1 is a formula applied when the spiral groove is formed with the outer peripheral side of the sliding surface as the base end, and Formula 2 is a formula applied when the inner peripheral side is formed with the base end, and in the present invention, The dam width ratio of the spiral grooves 10 and 11 is set to about 0.2 to 0.8. The optimum value of the dam width ratio varies depending on other parameters, for example, the type of intervening fluid, the rotation speed, etc., but a more preferable value is the dam width ratio of about 0.3 to 0.6. The dam width ratio can be changed between the rotating ring 3 and the non-rotating ring 4.

Here, the spiral groove in the present invention is about 2 to
It has a depth of 15 μm, and its width and angle of advancing angle are determined by the type of intervening fluid and the number of revolutions. In this embodiment, a spiral groove 10 having an advancing angle is formed on the sliding surface 5 of the rotating ring 3, and a spiral groove 11 having a receding angle is formed on the sliding surface 6 of the non-rotating ring 4. However, it is also possible to form the opposite relationship.

The pattern of the spiral groove is shown in FIGS.
The pattern is not limited to the one shown in FIG. Although not shown, the number of spiral grooves 10 or 11 having an advancing angle with respect to the relative rotation direction is set to be larger than that of the other in the forward rotation which is the normal rotation direction of the rotation shaft 2, or the width thereof is set. The spiral groove 11 or 10 having a receding angle with respect to the relative rotation direction is set to be wider than the other or deeper than the other so as to have a receding angle with respect to the relative rotation direction depending on the flow rate of pumping fluid between the sliding surfaces 5 and 6. On the contrary, the flow rate discharged is set to be small, and the pressure between the sliding surfaces 5 and 6 is set to be sufficiently higher than the pressure around the bearing (usually atmospheric pressure). Even when the spiral grooves 10 and 11 are formed in a perfect mirror image relationship, as in the present embodiment, in the planar shape of the spiral groove, the groove width at the inner end is narrower than the groove width at the open end. It was confirmed experimentally that the spiral groove having the advancing angle with respect to the relative rotation direction discharges less than the flow rate pumped between the sliding surfaces 5 and 6 by the spiral groove having the receding angle. ing.

The method of forming the spiral groove on the surface of the sliding surface is as follows: tungsten carbide, silicon carbide, silicon nitride,
After forming the rotating ring 3 and the non-rotating ring 4 into a predetermined shape with a material such as alumina ceramic or cemented carbide, a spiral groove is chemically, physically or electrochemically formed on the sliding surface. To form. For example, it can be formed by etching as a chemical method, shot blasting by spraying powder as a physical method, and various plating treatments as an electrochemical method.

Next, the second invention will be described with reference to FIGS. 4 and 5. The present invention, in addition to the configuration of the first invention described above, is such that a fluid is forcibly supplied between the sliding surfaces 5 and 6 so as to have a sufficiently low friction property even at low speed rotation. Is. Therefore, the same components as those described above are designated by the same reference numerals and the description thereof will be omitted.

The non-rotating ring 4 according to the present invention has a plurality of inlets 27 formed between the two O-ring grooves 26 formed on the outer peripheral end surface 20 thereof and a plurality of jets formed on the sliding surface 6. Conductor 2 having outlets 28, ... Formed in the non-rotating ring
The O-ring 30 is communicated with the O-ring groove 26 and the O-ring 30
Is fitted and can be hermetically fixed to the inner wall 18 of the housing 1. An annular groove is formed in the inner wall 18 of the housing 1 between the O-rings 30 to form an annular sealed space communicating with the inlets 27, ... Outside the outer peripheral end surface 20 of the non-rotating ring 4. 31 is formed, and a fluid supply path 32 for supplying a high-pressure fluid to the annular groove 31 is formed in communication with the housing 1.

Here, it is most preferable that the jet ports 28, ... Are opened on the flat surface 13 which is the sliding surface 6 of the non-rotating ring 4 and in which the spiral groove 11 is not formed, as shown in FIG. . The reason is that the high-pressure fluid supplied from the fluid supply path 32 to the annular groove 31 is ejected from each inlet 27 through each conduit 28 through the passage 29. This is because the pressure action of the fluid becomes larger as the distance between the two becomes smaller. Further, the jet ports 28, ...
As shown in FIG. 6, the sliding surface 6 of the non-rotating ring 4 is provided on the bottom surface of the annular flow path 33 which is formed deeper than the depth of the spiral groove 11 so as to intersect with the spiral groove 11. May be. In this case, the high-pressure fluid ejected from the ejection port 28 is uniformly supplied to the front surface of the sliding surface 6 through the annular flow path 33.

Next, the third invention will be described with reference to FIG. 7. In the present invention, in addition to the structure of the first invention described above, a fluid is forcibly supplied between the sliding surfaces 5 and 6, It has a sufficiently low friction property even at low speed rotation. Therefore, the same components as those described above are designated by the same reference numerals and the description thereof will be omitted.

According to the present invention, the first non-rotating ring 4a and the first non-rotating ring 4a are completely in a mirror image relationship on the inner wall 18 of the housing 1 with the rotating ring 3 fixed to the rotating shaft 2 interposed therebetween. It has a basic structure in which the second non-rotating ring 4b is attached in a sealed state. Here, the configuration corresponding to the first non-rotating ring 4a is denoted by a after the reference numeral, and the configuration corresponding to the second non-rotating ring 4b is denoted by a b after the reference numeral for distinction.

More specifically, two pairs of sliding surfaces 5a, 6a and 5b, 6b, which are in contact with the rotating ring 3 and the non-rotating rings 4a, 4b, respectively, are inwardly formed with their outer peripheral edges as base ends. Sliding surfaces 5a, 5b formed on both sides of the rotary ring 3 as the rotary shaft 2 rotates in the forward direction are provided with spiral grooves 10a, 11a and 10b, 11b which extend and are closed at their ends and which are substantially mirror images of each other. Or each non-rotating ring 4
The dynamic pressure is generated in the spiral groove of one of the sliding surfaces 6a, 6b formed on one surface of a, 4b, and the dynamic pressure is generated in the spiral groove of the other sliding surface with the reverse rotation. It will be.
In this embodiment, spiral grooves 10a and 10b having an advance angle with respect to the forward direction rotation are formed on both surfaces of the rotating ring 3, and the first non-rotating direction having a relative rotating direction opposite to the rotating direction is formed. The ring 4a and the second non-rotating ring 4b are formed with spiral grooves 11a and 11b having a backward angle with respect to the relative rotation direction.

A fluid supply passage 35 for supplying a high-pressure fluid is provided in an annular space 34 surrounded by the outer peripheral end surface 33 of the rotating ring 3, the step portions 9a and 9b of the non-rotating rings 4a and 4b, and the inner wall 18. It communicates with the inside of the housing.
That is, the high-pressure fluid supplied from the fluid supply passage 35 is
After the space 34 is filled, it is pumped between the sliding surfaces 5a and 6a and between the sliding surfaces 5b and 6b. Here, in order to attach the non-rotating rings 4a and 4b to the housing 1 in a sealed state, the outer peripheral end surfaces 20a and 20 of the non-rotating rings 4a and 4b are attached.
b, O-ring grooves 36a and 36b are formed in the
With the O-rings 37a and 37b fitted in the ring grooves 36a and 36b, the O-rings 37a and 37b are hermetically fitted to the inner wall 18 and the outer peripheral edge 25a of the first non-rotating ring 4a located inside the housing 1 is annularly stepped. The outer peripheral edge 25b of the second non-rotating ring 4b, which rests at 19 and is located outwardly, is clamped by the annular flange portion 24 of the annular fixture 22 with the pressing metal fitting 38 made of a leaf spring interposed. ing.

Finally, regarding the first invention, which is the common basic constitution of the present invention, a screw having an advancing angle on the sliding surface 5 of the rotary ring 3 with respect to the specific forward rotation direction of the rotary shaft 2. In the case where the wire groove 10 is formed, the spiral groove 11 having a receding angle is formed on the sliding surface 6 of the non-rotating ring 4, and both the spiral grooves 10 and 11 are formed in a perfect mirror image relationship,
The specific operation will be described below.

First, as shown in FIG. 8, when the rotary shaft 2 rotates in the forward direction at a high speed, the spiral groove 10 formed on the sliding surface 5 pumps the fluid between the sliding surfaces 5 and 6, Thereby, the inside of the sliding surface in the radial direction (near the end of the spiral groove 10)
, A dynamic pressure P _O1 is generated higher than the outside of the sliding surface, while
Since the spiral groove 11 formed on the sliding surface 6 of the non-rotating ring 4 has a receding angle with respect to the relative rotation direction of the non-rotating ring 4, the spiral groove 11 causes a gap between the sliding surfaces 5 and 6. The existing fluid is discharged to the outer peripheral side in the radial direction to reduce the pressure between the sliding surfaces 5 and 6, and as a result, the dynamic pressure P _O1 is changed to P _O as shown in the figure. _Since the peak value of _O is sufficiently high, it is possible to maintain a non-contact state between the sliding surfaces 5 and 6.

Next, when the rotating shaft 2 is rotated at a high speed in the opposite direction as shown in FIG. 9, the sliding surface 6 of the non-rotating ring 4 is rotated.
Since the spiral groove 11 formed at the front has an advancing angle with respect to the relative rotation direction of the non-rotating ring 4, the spiral groove 11 pumps the fluid between the sliding surfaces 5 and 6, thereby causing the sliding movement. A dynamic pressure P _I1 is generated inside the moving surface in the radial direction (near the end of the spiral groove 11) than outside the sliding surface, while the spiral groove 10 formed on the sliding surface 5 of the rotating ring 3 is The rotating ring 3
Since it has a receding angle with respect to the rotation direction of the
The fluid present between the sliding surface 5, 6 and discharged to the outer peripheral side in the radial direction, reducing the pressure between the sliding surface 5, 6, as a result, the dynamic pressure P _I1 to P _I as illustrated by Although changed, the peak value of the dynamic pressure P _I is sufficiently high, so that the sliding surfaces 5 and 6 can be maintained in a non-contact state.

The operation described above is for the case where the rotating shaft 2 is in the forward rotation or the reverse rotation at the time of operation in which the rotating speed has reached a sufficiently high speed, but the rotating speed is low at the initial stage of starting or immediately before stopping. When the dynamic pressure is low, the problem of increased frictional resistance can be solved by forcibly supplying the fluid between the sliding surfaces 5 and 6 as in the second or third invention. Further, when the bidirectional hydrodynamic bearing H of the present invention is used by incorporating it into a device that rotates only in the forward direction, even if abnormal reverse rotation occurs at the initial stage of start or immediately before stop, the sliding surfaces 5, 5 6
Since the fluid is pressure-fed between them, the sliding surfaces 5 and 6 are not firmly fixed in any case, and the sliding surfaces 5 and 6 are not worn or deteriorated due to frictional heat.

In addition, the rotating device equipped with the bidirectional dynamic pressure fluid bearing H of the present invention has a rotating shaft 2 at the time of operation in principle.
If the rotation direction of is only forward rotation,
In order to improve the dynamic pressure performance, it is desirable that the dynamic pressure by the spiral groove having an advance angle with respect to the relative rotation direction be as high as possible. In that case, the number of spiral grooves 10 or 11 having an advance angle with respect to the normal rotation direction is set larger than the other, the width thereof is set wider than the other, or the depth thereof is set deeper than the other. By doing so, it is possible to provide excellent sealing performance during forward rotation.

On the other hand, as in the case where the rotary shaft 2 is arranged in a penetrating state with respect to the housing 1 and the two-way hydrodynamic bearings H, H of the present invention are mounted facing each other at both ends thereof, a specific rotation is performed. In some cases, it is desired to make the bearing performance in the direction substantially the same as the bearing performance for rotation in the opposite direction. It has
It is conceivable to form the spiral grooves 10 and 11 so as to have a perfect mirror image relationship with each other, but depending on the shape of the spiral groove, even if they are formed in a perfect mirror image relationship, they can be rotated in forward and reverse directions. As described above, the same dynamic pressure performance may not be obtained in some cases. In that case, the plane shape of the spiral groove should be adjusted, or the number of grooves, groove width, and
It is possible in principle if the groove depth, groove length, etc. are adjusted to give a slight change from the perfect mirror image relationship.

[0043]

According to the bidirectional hydrodynamic bearing of the first aspect of the invention as described above, the sliding surfaces of the rotating ring fixed to the rotating shaft and the non-rotating ring fixed to the housing are in contact with each other.
The outer peripheral edge or the inner peripheral edge extends at the base end, and the spiral grooves that are close to each other and close to each other in a substantially mirror image relationship are provided, so that the relative rotation formed on one sliding surface as the rotating shaft rotates in the forward direction. Fluid is pumped between the sliding surfaces by the fluid transport action of the spiral groove having an advancing angle with respect to the rotation direction,
The pressure between the sliding surfaces can be increased sufficiently to reduce the frictional resistance between both sliding surfaces, and the relative rotation direction formed on the other sliding surface due to the reverse rotation of the rotating shaft. Similarly, due to the fluid transport action of the spiral groove having the advancing angle, the fluid is similarly forced between the sliding surfaces to generate dynamic pressure, and even when the rotation shaft rotates in the forward direction or the reverse direction, The rotating shaft can be supported by keeping the moving surface in a non-contact state. Therefore, even if reverse rotation occurs at the initial stage of rotation of the rotary shaft or immediately before stopping, the friction between the sliding faces increases due to the strong contact between the sliding faces, as in the conventional dynamic pressure gas bearing. There is no problem that heat is generated and the characteristics of the surface are impaired. Also, in order to support both ends of the rotating shaft that penetrates the housing, the arrangement of the rotating ring and the non-rotating ring in the axial direction of the rotating shaft is reversed, so conventionally, rotation in opposite directions is set to the forward direction. However, according to the present invention, even if the same bidirectional hydrodynamic bearing is mounted opposite to both ends of the rotary shaft, one spiral groove is formed relative to the relative rotational direction. Since they have the advancing angle, both of them have good bearing performance, and the cost can be reduced.

Further, the number of spiral grooves having an advance angle with respect to the relative rotation direction due to the forward rotation of the rotary shaft is set larger than the other, the width thereof is set wider than the other, or the depth thereof is set. By setting it deeper than the other, the bearing performance can be improved when the rotating shaft rotates only in the forward direction during normal operation, and even if the rotating shaft rotates in the opposite direction, both sliding The non-contact state can be maintained to such an extent that the surfaces do not come into solid contact with each other. When the spiral grooves formed on both the sliding surfaces are in a perfect mirror image relationship, a substantially similar non-contact state is obtained regardless of whether the rotating shaft rotates in the forward direction or in the reverse direction. It can be set so as to have bearing performance, the spiral groove can be easily processed, and the cost can be reduced.

According to the bidirectional hydrodynamic bearing of the second invention, in addition to the structure of the second invention, a plurality of inlets formed between two O-ring grooves formed on the outer peripheral end surface of the non-rotating ring. And a plurality of ejection openings opened on the sliding surface are communicated with each other through a conduction path formed in the non-rotating ring, and when the O ring is fitted into the O ring groove and hermetically fixed to the inner wall of the housing,
An annular groove is formed in the inner wall corresponding to both O-rings so as to form an annular sealed space communicating with each of the introduction ports outside the outer peripheral end surface of the non-rotating ring, and a fluid for supplying high-pressure fluid to the annular groove. Since the supply passage is formed to communicate with the inside of the housing, the fluid is forced to flow between both sliding surfaces, and the dynamic pressure generation performance due to the spiral groove is low. Can be maintained or the contact frictional resistance can be sufficiently reduced, and excellent bearing performance is achieved regardless of high speed rotation and low speed rotation.

In this case, if the jet outlet is formed on a flat surface which is a sliding surface and does not form a spiral groove, a high pressure fluid jetted from the jet outlet can efficiently form a fluid film between the sliding surfaces. Further, when the jet outlet is formed in the annular flow passage which is a sliding surface and intersects with each spiral groove and is formed deeper than the depth of the spiral groove, a high pressure is uniformly applied between the sliding surface through the spiral groove from the annular flow path. Fluid can flow in.

According to the bidirectional hydrodynamic bearing of the third invention, the first non-rotating ring and the second non-rotating ring are sealed in the inner wall of the housing with the rotating ring fixed to the rotating shaft interposed therebetween. The rotating ring is provided with spiral grooves, which extend from the outer peripheral edge as a base end and are closed at their ends, on both sliding surfaces of the rotating ring and the non-rotating rings that are in contact with each other. Since a fluid supply path for supplying high-pressure fluid to the space surrounded by the outer peripheral end face of each non-rotating ring and the inner wall is formed in communication with the housing, two pairs of both sliding surfaces from the outer peripheral end side of the spiral groove are formed. The fluid can be forced to flow in between, and it can be applied during low-speed rotation as described above.

In this case, the first non-rotating ring located inside the housing is stopped by the stepped portion provided on the inner wall, and the second non-rotating ring located outside is pressed inward. By interposing a pressing metal fitting consisting of a spring on the outer peripheral edge of the second non-rotating ring and mounting it on the housing with an annular fixing tool, the gap between the two sliding surfaces can be automatically adjusted. is there.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing a mounted state of a bidirectional hydrodynamic bearing of the first invention.

FIG. 2 is a plan view showing an example of a spiral groove pattern formed on the sliding surface of the rotating ring used in the first invention.

FIG. 3 is a plan view showing an example of a spiral groove pattern similarly formed on the sliding surface of the non-rotating ring.

FIG. 4 is a sectional view of an essential part showing a mounted state of a bidirectional hydrodynamic bearing of the second invention.

FIG. 5 is a plan view of a non-rotating ring used in the second invention.

FIG. 6 is a plan view of a non-rotating ring having another structure.

FIG. 7 is a cross-sectional view of essential parts showing a mounted state of a bidirectional hydrodynamic bearing of the third invention.

[Fig. 8] Pressure distribution diagram between sliding surfaces during forward rotation

FIG. 9 is a pressure distribution diagram between sliding surfaces during reverse rotation.

[Explanation of symbols]

H bidirectional hydrodynamic bearing 1 housing 2 rotating shaft 3 rotating ring 4 non-rotating ring 4a first non-rotating ring 4b second non-rotating ring 5 sliding surface 6 sliding surface 7 center hole 8 center hole 9 step 10 screw Wire groove 11 Spiral groove 12 Flat surface 13 Flat surface 14 Annular step portion 15 Fixing sleeve 16 Fastening tool 17 Screw portion 18 Inner wall 19 Annular step portion 20 Outer peripheral end surface 21 End surface 22 Annular fixing tool 23 Bolt 24 Annular flange portion 25 Outer Edge 26 O-ring groove 27 Inlet port 28 Jet port 29 Conducting path 30 O-ring 31 Annular groove 32 Fluid supply path 33 Annular flow path 34 Space 35 Fluid supply path 36 O-ring groove 37 O-ring 38 Press fitting P _{O1 in} forward rotation dynamic pressure by spiral groove having a forward angle in Zendo圧P _I1 reverse rotation in the dynamic pressure P _O forward rotation by spiral groove having a forward angle Zendo圧in _I reverse rotation

Claims (11)

[Claims] 1. A substantially mirror image in which both outer peripheral edges or inner peripheral edges of the rotary ring fixed to a rotary shaft and a non-rotating ring fixed to a housing are in contact with each other and the ends thereof are closed. Related spiral grooves are provided respectively, and dynamic pressure is generated in the spiral groove of one sliding surface with forward rotation of the rotary shaft, and dynamic pressure is generated in the spiral groove of the other sliding surface with reverse rotation. A bidirectional hydrodynamic bearing characterized by being generated. 2. The dam width ratio of the spiral groove is about 0.2-0.
8. The bidirectional hydrodynamic bearing according to claim 1, wherein the hydrodynamic bearing is set to 8. 3. The bidirectional hydrodynamic bearing according to claim 1, wherein the number of spiral grooves having an advancing angle with respect to a relative rotation direction due to forward rotation of the rotation shaft is set to be larger than the other. 4. The bidirectional hydrodynamic bearing according to claim 1, wherein the width of the spiral groove having an advancing angle with respect to the relative rotation direction due to the forward rotation of the rotary shaft is set wider than the other. 5. The bidirectional hydrodynamic bearing according to claim 1, wherein the depth of the spiral groove having an advancing angle with respect to the relative rotation direction due to the forward rotation of the rotary shaft is set deeper than the other. . 6. The bidirectional hydrodynamic bearing according to claim 1, wherein the spiral grooves formed on the both sliding surfaces have a perfect mirror image relationship. 7. A substantially mirror image in which the outer peripheral edge or the inner peripheral edge extends toward the two sliding surfaces of the rotary ring fixed to the rotary shaft and the non-rotating ring fixed to the housing, which are opposed to each other, and the end ends are closed. Related spiral grooves are provided respectively, and dynamic pressure is generated in the spiral groove of one sliding surface with forward rotation of the rotary shaft, and dynamic pressure is generated in the spiral groove of the other sliding surface with reverse rotation. A bidirectional hydrodynamic bearing generated by
A plurality of inlets formed between two O-ring grooves formed on the outer peripheral end surface of the non-rotating ring and a plurality of jet outlets formed on the sliding surface communicate with each other through a conduction path formed in the non-rotating ring;
When the O-ring is fitted into the O-ring groove and hermetically fixed to the inner wall of the housing, both O-rings are formed outside the outer peripheral end surface of the non-rotating ring so as to form an annular sealed space communicating with the inlets.
A bidirectional hydrodynamic bearing characterized in that an annular groove is formed in the inner wall corresponding to the space between the rings, and a fluid supply path for supplying a high-pressure fluid to the annular groove is formed in communication with the housing. 8. The bidirectional hydrodynamic bearing according to claim 7, wherein the jet outlet is formed on a flat surface which is a sliding surface and does not have a spiral groove formed therein. 9. The bidirectional hydrodynamic bearing according to claim 7, wherein the jet outlet is provided in an annular flow path which is a sliding surface, intersects with each spiral groove, and is formed deeper than the depth of the spiral groove. 10. A first non-rotating ring and a second non-rotating ring are hermetically attached to the inner wall of the housing with a rotating ring fixed to the rotating shaft interposed therebetween, and the rotating ring and each non-rotating ring are paired with each other. The two sliding surfaces that contact each other are provided with spiral grooves that extend from the outer peripheral edge as a base end and are closed at their ends and that are in a substantially mirror image relationship with each other, and are formed on both sides of the rotating ring as the rotating shaft rotates in the forward direction. Dynamic pressure is generated in the spiral groove of one sliding surface of the dynamic surface or the sliding surface formed on one surface of each non-rotating ring, and dynamic pressure is generated in the spiral groove of the other sliding surface with reverse rotation. A bidirectional hydrodynamic bearing comprising: a fluid supply passage communicating with the housing, the fluid supply passage supplying high-pressure fluid to a space surrounded by the outer peripheral end surface of the rotating ring, each non-rotating ring, and the inner wall. A bidirectional hydrodynamic bearing. 11. A leaf spring for stopping a first non-rotating ring located inside the housing against a step portion provided on an inner wall and pressing a second non-rotating ring located outside inward. 11. The bidirectional hydrodynamic bearing according to claim 10, wherein a pressing metal fitting made of is interposed in the outer peripheral edge of the second non-rotating ring and is attached to the housing by an annular fixing tool.